The prediction of the stability of fluidized beds (Batchelor, 1988) has required the use of new physical characteristics, such as the hydrodynamic dispersion coefficient and the elasticity of the suspension. In this thesis, those characteristics have been measured on model solid-liquid suspensions (quasi-monodisperse glass beads in "water-like" liquids), in simplified experimental conditions. The experiments have been performed in a fluidized bed (a suspension stabilized by a counterflow), allowing the control of the concentration by the flow-rate of the injected fluid. The concentration has been determined by an acoustic technique (based on the measurement of the sound velocity), with an accuracy of about 0.1% on the whole range (0
